This invention relates to diagnostic techniques of characterizing blood flow through the heart by detecting radioactivity from a radioactive blood pool tracer injected into the patient's bloodstream and displaying the resultant data. More specifically, it relates to the use of a moveable cursor display to locate data of interest and the use of a microcomputer to calculate certain indices of heart performance in the course of characterizing blood flow through the heart.
The characterization of blood flow through the heart using radioactive blood pool tracers injected into the patient's bloodstream is well known in the art. Illustrations of the application of this principle are found in Belgian Pat. No. 848072 and the article by Wagner, et. al., "The Nuclear Stethoscope: A Simple device for Generation of Left Ventricular Volume Curves", The American Journal of Cardiology, Volume 38, Nov. 23, 1976, pp. 747-750.
Other pertinent literature references include:
Hoffman, G., and N. Kleine: "The Method of Radiocardiographic Function Analysids:" ("DIe Methode der radiokardiographischen Funktionsanalyse"), Nuclear-Medizin, Vol. 7, pp. 350-370, 1968.
Bacharach, S. L., et. al., "Gated Scintillation Probe Measurement of Left Ventricular Function", Transactions of the American Nuclear Society, Vol. 22: 117, 1975.
Bacharach, S. L., et al., "An ECG-gated scintillation probe-minicomputer system for real-time construction and analysis of high temporal resolution left ventricular volume curves", Journal of Nuclear Medicine, Vol. 17: 557, 1976.
Nickloff, E. L., Thesis: "The Physics of Left Ventricular Performance Measurements with Radioactive Tracers", School of Hygiene and Public Health of the Johns Hopkins University, January 1977.
As illustrated in the Belgian patent and the Wagner article, blood flow through the heart may be characterized by injecting a radioactive blood pool tracer into the patient's bloodstream and detecting resulting changes in radioactivity from the heart as it contracts and expands. Typically, a radiation detector is located adjacent to the patient's chest wall in order to monitor radiation from the left ventricle of the heart. In order to synchronize the acquisition of data to the patient's heartbeat, the patient is connected an electrocardiogram apparatus. The patient's heartbeat interval is divided into a plurality of shorter temporal subintervals. The number of radiation counts associated with each subinterval is detected and stored. Radiation counts are detected during successive heartbeats and the counts are added to the counts previously detected during each of the corresponding subintervals. The resultant data are cumulatively stored in memory. The memory contents are repeatedly displayed on a CRT screen. This display is in the form of a bar graph in which the peaks vary in amplitude as a function of time proportional to the changing volume of the left ventircle. After the desired number of heartbeats have occurred, a photograph is taken of the CRT display.
Similarly, the radiation detector is relocated to a suitable position on the patient's chest wall in order to measure the radiation from local body tissues in the vicinity of the heart. This radiation is commonly referred to as background radiation. Radiation counts are detected and accumulated as in the case of radiation from the left ventricle of the heart. Again, after the desired number of heartbeats have occurred, a photograph is taken of the CRT display.
At this point manual measurements are taken of the photographic data in order to calculate useful performance indices of the heart function such as ejection fraction, etc.
It is apparent that the major disadvantage and limitation of the conventional blood flow characterization method is the need for manual measurements of photographic data. This technique is time-consuming, expensive and the quality of the output varies with the skills of the technician.
Accordingly, it is an object of the invention to provide an atuomated method of obtaining various performance indices of heart function.
It is a further object of the invention to provide a real-time method for locating the left ventricle of the heart and for locating a suitable position for measuring tissue background activity in proximity to the heart.
It is still a further object of the invention to provide improved apparatus for atuomatically obtaining various performance indices of heart function.